1. Field of the Invention.
The present invention relates generally to fluid-operated switches generally and, more particularly, to such a switch that is adjustable to provide selective actuation over a range of either pressure or vacuum.
2. Background Art.
"Pressure", as used herein, will be understood to mean gage pressure, or pressure above atmospheric pressure, and "vacuum", as used herein, will be understood to mean s pressure less than atmospheric pressure, with "increasing vacuum" meaning pressure closer to zero absolute pressure.
Fluid-operated switches are well known devices which usually include a diaphragm one side of which communicates with a fluid under pressure or vacuum. The fluid may be any of a wide range of gases or liquids. On the other side of the diaphragm are means operatively connected between the diaphragm and switching means such as an electric switch. When the diaphragm is flexed by a change in the pressure or vacuum such that the change causes the fluid-operated switch to reach a set point, the electric switch is activated to make or break an electrical contact. Such fluid-operated switches are manufactured, for example, by Whitman Controls, of Bristol, Conn.
Although some conventional fluid-operated switches have fixed set points, many are constructed to be adjustable over a range of either pressure or vacuum and may be constructed to be field adjustable; that is, the user may selectively change the set points. In some cases, the housing of a given switch may be used in either pressure or vacuum applications, but the internal components are specific to one application or the other and must be changed, usually by the manufacturer, when it is desired to employ the switch in a different application from that for which it was originally constructed. Known conventional fluid-operated switches do not permit the user to employ them in either pressure or vacuum applications by convenient field adjustment.
Accordingly, it is a principal object of the present invention to provide a fluid-operated switch which may be field-adjusted to permit use in either pressure or vacuum applications without changing internal elements.
Another object of the invention is to provide such a switch which is easily and economically manufactured.
Other objects of the invention, as well as particular advantages and features thereof, will, in part, be obvious and will, in part, be apparent from the following description and the accompanying drawing figures.